The Role of Language in Design
A "language" can be seen as a a collection of named abstractions (e.g. of a computing model, of the real world) and a set of protocols for combining the abstractions in meaningful ways.
Choose the wrong abstractions or the wrong protocol and you can`t say what you want to say (e.g. specify, describe), or you have to "translate" what you want to say into a "foreign language" and then the person(s) you are working with have to understand it and translate it back... hopefully understanding what you meant!